IMPROVEMENT OF EVALUATION METHOD FOR ROCK MASS STRENGTH BY NONLINEAR MULTI-SCALE ANALYSIS

改进了一种基于多尺度分析的不连续岩体强度评价方法。岩体中的裂隙、节理等不连续面被视为薄层，用普通实体有限元模拟，从而可以利用岩体表面的图形图像进行分析。在石膏砂浆试件的一系列压缩试验中，仔细观察了裂纹闭合的非线性应力应变关系，并将其非线性关系表示为本构关系。裂纹用具有非线性本构关系的薄层来表示，而不是复杂的接触分析模型，裂纹的非线性闭合和张开行为用其刚度的硬化和软化来表示。因此，仅从完整岩石的裂隙分布和力学性质的图形图像出发，采用薄层模型就能较好地模拟含有多个裂隙的岩体的非线性变形行为。此外，还利用原-对偶优化公式开发了功能强大的极限载荷分析程序，并将其融入薄层分析系统中。从而建立了非连续岩体非线性多尺度分析系统的原型。对裂隙石膏砂浆试件的直剪试验和现场实际岩体抗剪试验进行了验证分析。结果与测量结果吻合较好，说明了多尺度分析系统的有效性。

A strength evaluation method based on the multi-scale analysis for discontinuous rock mass has been improved. Discontinuities in rock mass such as cracks and joints are treated as thin layers and modeled by ordinary solid finite elements, which enables utilization of graphical image of rock mass surface in the analysis. Nonlinear stress-strain relation of crack closing has been carefully observed in a series of compression tests of gypsum mortar specimen, and their nonlinear relation has been formulated in a form of constitutive equation. Cracks are represented by thin layers with the nonlinear constitutive law, instead of complicated contact analysis model, and their nonlinear closing and opening behaviors are expressed by hardening and softening of its stiffness. The nonlinear deformation behavior of rock mass that includes many cracks are therefore appropriately simulated by suing the thin layer model only from graphical image of crack distribution and mechanical properties of intact rocks. In addition, a powerful limit load analysis has also developed by utilizing formulation of the primal-dual optimization and incorporated into the thin layer analysis system. Thus the nonlinear multi-scale analysis system for discontinuous rock mass has been made in a form of prototype. Validation analyses have been done for direct shear test of cracked gypsum mortar specimen and an actual rock mass shearing test in site. Results agreed with measurements fairly well, and revealed the validity of the multi-scale analysis system.